1. Field of the Invention
The invention relates to a method of planar orienting of cholesteric liquid crystals free from faulty inclination between the two parallel plates of a liquid crystal cell. The invention also relates to means for working the method.
2. Description
In the case of cholesteric liquid crystals used in optical components, particularly in optical filters, a liquid crystal layer has to be given a uniform planar orientation between the two parallel plates of a liquid crystal cell. "Planar" as used in this description means either molecule arrangements parallel to the plate or arrangements in which the molecules have a so-called tilt angle of up to 30.degree. C.
During manufacture of these cells, focal-conical faulty inclination lines occur, e.g. as a result of flow orientation or cooling of the liquid crystal from the isotropic phase. As a result of these faulty inclination lines, incident light is scattered. The scattered light is also depolarized and thus reduces the filtering or polarizing efficiency of cholesteric liquid crystal filters (compare Jpn. J. Appl. Phys., Vol. 29, No. 10, 1990, pages 1974-1984, particularly page 1975).
The appearance can be improved by cutting the glass plates, but this method does not completely eliminate the faulty inclination lines and is also impracticable on a production scale.